Engine exhaust testing and monitoring devices are used in exhaust emissions compliance testing and verification. These devices can be stationary, which requires that a vehicle being tested be brought to the testing device and tested while the vehicle is also stationary. Other devices are portable and can be temporarily installed on and carried by a vehicle during testing, which allows the vehicle to be tested under actual use conditions while moving. The Portable Emissions Monitoring Systems (PEMS), which are in use today, tend to be expensive and complex. There is value having a self-contained, portable, and reliable system for exhaust emissions testing.
U.S. Pat. No. 7,805,986 is directed to a portable vehicle exhaust flow sensor. This system measures mass flow and gas temperature, and includes an instrumented pipe 20 that is attached to the vehicle exhaust pipe (FIG. 1) and has a processor to which the sensor cables are connected. The processor case can be mounted to the pipe (See, column 4, lines 44-46). The system lacks specific description of other sensors for measuring additional gas properties or constituents, but discloses generically a gas analyzer that may be connected to the pipe.
U.S. Pat. No. 6,148,656 shows a device having a pipe having a mass flow sensor and temperature sensor that connects to the vehicle exhaust and an electronic unit mounted to the pipe. This system includes a gas analyzer 30 for measuring gas constituents that is carried elsewhere on the vehicle, so it is not self-contained.
The invention provides a simple, low-cost, portable, self-contained unit to evaluate NOx and PM exhaust emission compliance along with other exhaust characteristics.
An exhaust emissions monitoring device according to the invention includes a pipe adapted to mount to the tailpipe of a vehicle. The pipe defines an internal flow passage to allow exhaust to flow through. A plurality of sensors is mounted on the pipe and each sensor extends through an access port in the pipe wall to be exposed to the internal flow passage. Exhaust properties and constituents are sensed by multiple sensors for each constituent, i.e., there are two or more sensors for each of oxides of nitrogen (NOx), temperature, ammonia, particulate matter, etc. The sensors are connected to a controller, which includes a data logger and a microprocessor.
The controller includes a cable for connecting to the vehicle engine control unit (ECU) and power system.
According to one embodiment, the device includes a hollow cylinder carrying sensors exposed to a central passageway, wherein, there are multiple sensors for each of the monitored exhaust constituents (gas temperature, NOx, ammonia, particulate matter), the sensors being connected to a data logger/processor mounted to the cylinder, and a cable to connect the data logger/processor to the vehicle engine control unit (ECU) for receiving vehicle operation data (engine speed, load), for receiving operating power for the processor and sensors, and to communicate with the OBD system to report emissions data.
The use of multiple sensors makes the device able to self-diagnose faults. In addition, multiple sensors make the system output less sensitive to variability of a particular sensor or the failure of a particular sensor.